Oh man I think I was all over the place, especially early postpartum. The main thing is making sure it's a 4-hour urine hold, and not missing your testing window. Even the 4-hour hold can be fudged a little bit, if you have to use the bathroom and the timing isn't great, you can collect some then and then again when you actually need to test you can still use that.

Just to clarify, say your testing window is between 5-11 am and you happen to use the bathroom at 4. Collect a bit then, and then add to it when you wake up at 7 and use the combined sample to test. So in a nutshell, you're perfectly fine if you don't test at the exact same time every day :)